A Norwegian University of Science and Technology study released Thursday found electric vehicles have a potential for higher eco-toxicity and greenhouse impact than conventional cars. The study includes an examination of the electric car’s life cycle as a whole rather than a study of the electric car’s environmental impact during the use phase.

A Nissan Leaf electric car recharging at an on-street public charging station in Amsterdam

The researchers conducted a comparison of the environmental impact of electric cars in view of different ratios of green-to-fuel electricity energy sources. In the case of mostly coal- or oil-based electricity supply, electric cars are disadvantageous compared to classic diesel cars with the greenhouse effect impact being up to two times larger.

The researchers found that in Europe, electric cars pose a “10% to 24% decrease in global warming potential (GWP) relative to conventional diesel or gasoline vehicles”.

The researchers suggest to improve eco-friendliness of electric vehicles by “reducing vehicle production supply chain impacts and promoting clean electricity sources in decision making regarding electricity infrastructure” and using the electric cars for a longer time, so that the use phase plays a more important role in the electric vehicle life cycle.